Streptococcus mutans refers to an anaerobic, gram-positive round bacterium that is usually located in the oral cavity and substantially contributes to tooth decay. It belongs to a larger species of Streptococci, though the group name is informal and describes the general bacteria within the genus. Streptococcus mutans and the related species of Streptococcus sobrinus exist habitually in the human mouth and can cause the manifestation of oral disease. While the presence of Streptococcus mutans in the human oral cavity is a natural occurrence, its interaction with other bacteria or propensity to form diverse colonies in different areas of the mouth makes it a detiemtn to oral health. For instance, it is the symbiotic exchange between Candida albicans and Streptococcus mutans that leads to the production of glucan and the formation of biofilm. While all streptococci can be divided into harmful and non-harmful types, even commensal varieties may become pathogens that lead to disease. It is the imbalances in microbial populations that frequently result in oral disease which is why all popular treatments aim to decrease levels of Streptococcus mutans.
Streptococcus mutans adheres to the dental hard tissues and other organisms by the cell-to-cell process. Bacterial growth on the teeth forms a biofilm, also called the dental plaque (1). The bacteria group utilizes the enzyme glucansucrase to change sucrose into dextran-based polysaccharide, a sticky and extracellular material that coalesces into plaque. Streptococcus mutans contribute to tooth decay by metabolizing sucrose to lactic acid (2). Mineralized tooth enamel which is vulnerable to decay comes as the result of the acidic environment. The subsequent interaction of the vulnerable plaque and accumulating lactic acid leads to prominent tooth decay and infection.
Dental plaque can be considered the precursor to tooth decay. While the plaque itself may be made of a variety of organisms, the interactions between it and the functions of Streptococcus mutans are often those that lead to the most health hazards. The dental plaque adheres to the teeth due to the bacterial cells while the biofilm clings to the surface of the teeth. Exposure to toxic elements from medicine, tobacco, or food additives often causes imbalances in Streptococcus mutans. As Streptococcus mutans develops and grows in the biofilm, the cells are able to maintain a balanced metabolism and have the potential to develop toxic compounds. This microbial community in the biofilm may reduce the growth of other competing bacteria. Streptococcus mutans has successfully evolved to be a dominant force in the development of the bacteria, and as such, its growth can determine oral health.
As illustrated in the diagram, Streptococcus mutans utilize the production of glucan and glucan binding proteins to form and observe influence over the biofilm. Adhesin interacts with the salivary pellicle, the only layer above the surface of the teeth. Sucrose is transformed into a polysaccharide that helps create the sticky which can directly build the dental plaque. Following this, increases in acidity as a result of additional functions of Streptococcus mutans or toxic materials can lead to the adhesion of the bacterium to the salivary pellicle and alter, the tooth surface. This can be detrimental to the health of the tooth as unbalanced and high populations of Streptococcus mutans may continue the process of plaque formation and increase the acidity in ecological niches of the mouth. The acidity directly contributes to the decay of the teeth.
Continued acidic conditions in the mouth encourage the growth and spread of acidogenic and aciduric bacteria as they are able to survive in areas that have low pH. Meanwhile, the acidity also erodes the surface of the teeth and creates the conditions for dental caries to spread. Due to the role Streptococcus mutans plays in the formulation of the biofilm and its contribution to the acidic environment, it is considered to be a catalyst and hazard for the initiation of dental caries and decay. Streptococcus mutans thrive in low pH conditions, and as such, continued maintenance of such environments continues to assist the development of a dental plaque, the erosion of the surface of the teeth, and the opportunity for the development of dental caries.
The leading management for infections as a result of Streptococcus mutans pathogenesis includes the use of Antibacterial mouthwashes that have chlorhexidine gluconate. This is because such mouthwashes work to reduce the population of Streptococcus mutans in the oral cavity significantly (3). Certain antibiotics such as cefotaxime cefazolin, methicillin, ampicillin, and clindamycin have also proven to be effective in decreasing the resistance rates of Streptococcus mutans. The reduction of sugars and other potentially dangerous factors from diets can also contribute to less frequent infections and healthier teeth.
Newly developed drugs, both natural and synthesized, have also become more viable in the treatment of Streptococcus mutans infections. Plant-derived medicine has shown to have antimicrobial, anti-inflammatory, and antibiofilm effectiveness within the oral cavity. The most prominent substances included α-mangostin or lawsone methyl (4). Cell leakage occurred as the result of Lupinifolin from Albizia myriophylla wood implementation during therapeutic treatment and management of the infection. A. gratissima and L. sidoides were cited to decrease biofilm integrity by causing a reduction of extracellular polysaccharides and bacteria (5). Overall, effective treatment for the pathogenesis and infection of Streptococcus mutans continues to be developed.
References
Lemos JA, Palmer SR, Zen L, Wen ZT, Kajfasz JK, Freires IA, et al. The Biology of Streptococcus mutans. Microbial Specter. 2019;7(1).
Ito S, Misaki T, Naka S, Wato K, Nagasawa Y, Nomura R, et al. Specific strains of Streptococcus mutans, a pathogen of dental caries, in the tonsils, are associated with IgA nephropathy. Scientific Reports. 2019;9(1).
Pokala P. Antibacterial Mouthwashes, Diet Can Reduce Tooth Decay [Internet]. San Diego (CA): Rady Children’s Hospital; (2022).
Salehi B, Kregiel D, Mahady G, Sharifi-Rad J, Martins N, Rodrigues C. Management of Streptococcus mutans–Candida spp. Oral Biofilms’ Infections: Paving the Way for Effective Clinical Interventions. Journal of Clinical Medicine. 2020;9(2):517.
Ben-Zaken H, Kriatman R, Coppenhagen-Glazer S, Khalifa L, Alkalay-Oren S, Gelman D, et al. Isolation and Characterization of Streptococcus mutans Phage as a Possible Treatment Agent for Caries. Viruses. 2021;13(1):1-19.